Paraffin wax composition for paper coating and process of making same



MLM! July 24, 1956 S. F. PERRY ETAL PARAF'FIN WAX COMPOSITION FOR PAPERCOATING ,AND PROCESS OF MAKING SAME Filed June 12, 1952 u] 2 m 12 g 1 s#6 *0 T 0 2w smpbeaw errz f fierm cw. J. 'ZoeLLer @ESWJYYICLM @aveatorCltbor'aczs PARAFFIN WAX CUMPOSHTHON FOR PAPER COATlNG AND PRQCESS OFMAKING AME Stephen F. lerry, Westfield, and Herman J. Zoeller,

Union, N. 3., assignors to Esso Research and Engineering (Zompany, acorporation of Delaware Application June 12, 1952, Serial No. 293,176

4 (Ilaims. (Cl. 196-17) The present invention is concerned with animproved wax composition which is particularly adapted for the coatingof fibrous substances such as paper and the like. In accordance with thepresent invention, an improved wax composition is secured by theblending of a narrow cut distilled refined wax with a wide cut sweatedrefined wax. Preferred compositions are secured when the average meltingpoints of the respective fractions are approximately equivalent. The waxcomposition of the present invention has a high blocking point and ahigh tensile strength, a combination not secured in either componentalone.

In the refining of hydrocarbon oils such as petroleum oils, it is knownto segregate parafiin waxes from so-called paraifin distillates, waxylubes and the like. The segregation of these waxes is secured by anumber of processes. For example, it is known to chill the selected waxcontaining fraction in order to secure crystallization of the wax and toremove the wax crystals from the oil by filtering, centrifuging and thelike. it is also known to use various dewaxing solvents such as liquidnormally gaseous hydrocarbons, such as propane, as well as othersolvents, such as methylethyl ketone and the like. It is also known toutilize in dewaxing operations solvent mixtures wherein one solventcomprises a wax precipitating solvent while the other comprises asolvent having a high solubility for oil. A solvent mixture of thischaracter, for example, comprises 60% by volume of toluene and 40% byvolume of methylethyl ketone. In utilizing a mixture of this character,it has been the practice to add the mixture in toto or incrementally tothe waxy distillate as it is being chilled. In dewaxing operations, itis also known to use various filter aids and other agents in order torender the dewaxing and filtering operations more efiicient.

The wax segregated from the hydrocarbon oil, usually termed slack wax,contains from about 10% to 40% of oil. The slack wax is refined usuallyby conventional sweating to produce crude scale wax in a manner toreduce the oil content to less than about 5% by weight. The slack waxmay be distilled to obtain the desired boiling range wax prior tosweating, if desired. This crude scale wax generally has an oil contentof about 2% to 3% by weight. In order to remove this oil from the scalewax to produce a refined wax having an oil content below about .5%,usually below about .3 various procedures have been proposed andemployed.

It is also known in the art to prepare wax compositions adapted forvarious commercial uses by blending various fractions and the like. Forexample, in the manufacture of wax compositions suitable for the coatingof paper, it

2,756,180 Fatented July 24, 1956 is essential that the wax have a hightensile strength and also have a high blocking point.

The tensile strength is determined by a Tinius Olsen machine. The wax tobe tested is heated to about 230 F. with constant stirring to remove alltraces of moisture. The hot wax is poured into dumbbell shape flatmolds, filling each mold as full as possible without overflowing. Thefilled molds are allowed to age for two hours in a constant temperatureF.) controlled humidity (50% room. The wax briquettes which have across-sectional area of 4 sq. in. at the narrow, center section, areremoved from the molds without distorting and placed in a water bath at70 F. before testing. Each briquette is placed in the holder at the baseof the balance on the Tinius Olsen machine and sufiicient tensionapplied to the briquette to allow the pointer arm to coincide with therest point. The tension applied is equal to about 2.5 lbs.,

The shot control slot is forced open and the shot allowed to flow into apan resting on a scale. At the instant of rupture the flow of shot willbe cut oil automatically. The weight of shot is recorded. A total ofeight briquettes are ruptured in this manner and those results whichcheck within 10% are averaged. The final average value is added to thecorrection for balancing the beam (2.5 lbs). This sum is multiplied byfour and the result is expressed as tensile strengthlbs./ sq. in.

The wax blocking test is made as follows:

Two-inch wide strips of breadwrap paper (25 lb./rearn) are hand coatedwith wax at about F. and then chilled in a water bath at 4-055 F. togive a wax consumption of about 20 to 30 lbs. of wax/ream. The waxedstrip is folded end to end and cut 17 /2" from fold. A one-inch widecenter slice is cut from the folded strip. The waxed paper specimen isinserted between two unwaxed paper strips and placed on the blockingplate (a metal plate across which a temperature gradient is maintained),with the folded end on a prescribed line at the hot end of the plate.Pressure is applied to each strip by covering it with a one-inch squaresteel bar, cushioned by sponge rubber pads so as to apply the pressureevenly. After exposure on the blocking plate for seven hours, the stripsare removed, cooled and carefully pulled apart starting at cool(unfolded) end. The distance to the beginning of the area of completeblocking (fusing together of the wax) is measured from either end of thestrip. This distance is converted to the blocking temperature by meansof a calibration curve relating temperature to distance along the plate.Average blocking values on a given wax generally agree within 1 F, witha maximum difference of 2 F. This test is conducted in a room held atconstant temperature (7073 F.) and constant humidity (50%).

A high blocking point is desirable since this is a measure of theminimum temperature at which the wax coated paper sticks when two sheetsare held together under pressure and then pulled apart. Wax surface ismarred at the blocking point or higher temperature. The narrow theboiling point and melting point range of the distilled product, thehigher the blocking point of the wax coated paper stock.

Associated with increased blocking point, attributed to the narrow cutparafiin wax, there is also a considerable decrease in the tensilestrength of the wax. A high tensile strength is desirable from a salesappeal and consurners point of view since tensile strength appears to berelated to the durability of the wax surface on the paper. That is, thehigher the tensile strength of the wax and more scuff resistant the waxsurface and the higher the sealing strength of the paper, with noflaking off on the cut edge. A wide cut paraffin wax possesses goodtensile strength but has a low blocking point.

Both desirable properties can be attainedto a considerably greaterdegree in a new product by a process whichinvolves the blending .of thenarrow cut distilled wax with a wide cut sweated wax preferably of thesame average melting point. i r a The present invention will be morefully appreciated by reference to the drawing illustrating oneembodiment of t e same- Refe'rring specifically. to the drawing, a waxycrude oil is introduced into distillation zone 1 by means of feed line2. Temperature and pressure conditions in zone 1 are adapted to removeoverhead by. means of lines 3 and 4 low boiling hydrocarbon fractions. Awaxy distillate fraction is removed as a side stream by means of line 5,while a residual oil is removed by means of line 6.

The waxy distillate is mixed with solvent introduced by means of line 40and flows through a chilling zone 7 which may comprise a plurality ofchilling stages wherein the temperature of the, waxy distillate isprogressively reduced. A typical operation is to introduce the feed oilinto an initial chilling stage at a temperature of about 130 F.; tointroduce the feed oil into the second chillin}; stage at a temperatureof about 90 F.; to introduce the feed oil to the third chilling stage ata temperature of 60 F to introduce the feed oil to the fourth chillingstage at a temperature of about 25 F. and to chill the same in thefourth chilling stage to a temperature inthe range from about to +10 F;

The operation of the respective chilling stages may be variedappreciably and either direct or indirect chilling means utilized. Forpurposes of illustration, it is assumed that a solvent mixture is usedand that the waxprecipitant comprises methylethyl ketone and that thearomatic solvent having a high solubility for oil comprises toluene. Itis also assumed that 3 to 4 volumes of total solvent mixture is utilizedper volume of waxy oil being dewaxed. The solvent mixture comprises 75%by volume of methylethyl ketone and 25% by volume of toluene. The waxcrystals in a slurry of solvent and oil are passed to filtering zone 8wherein the solid wax particles are segregated from the oilyconstituents and solvent by any suitable filtering .or separation means.The filtering zone may comprise drum filters, plate-and-frame presses,centrifuges or suitable equivalent equipment for the separation of theprecipitated waxy constituents from the oily constituents. The oil and aportion of the solvent is removed from zone 8 by means of line 9 and thewax cake .is preferably washed with a wash solvent introduced intofiltering zone 8 by means of line 10. Slack wax and solvent are removedfrom zone 8 by means of line 11 and passed to a distillation zone 12wherein a separation is made between the wax and the solvent. It is tobe understood that other means of separating the solvent from the waxmay beutilized if desirable.

The wax substantially free of solvent is removed from distillation zone.12 by means of line 13. The solvent mixture comprising methylethylketone and toluene is removed overhead from zone 12 by means of line 14and preferably, recycled to the system. Theoil-solvent mixture removedfrom filtering zone 8 by means of line 9 is introduced into adistillation zone wherein a separation is made between the oilyconstituents and the solvent mixture.

While the drawing illustrates a solvent dewaxing op.-

also be separated in a conventional plate-and-frame pressing operation.The slack wax may be further refined to crude scale wax in zone 15,which comprises a conventional sweating operation, or solvent deoilingopera tion, or the like. The oil removed from zone 15 by means of line30 may preferably be recycled to zone 7. The scale wax is removed fromzone 15 by means of line 35 and may be further refined by treatment withsulfuric acid or fullers earth, bauxite or other absorbent materials, orby hydrogenation under mild treating conditions.

The scale wax removed from sweating zone 15 containing from about 2% to3% of oil by weight is passed by means of line 35 to a sweating ordeoiling zone 36 wherein the oil content is reduced below about .5%,usually to below about 3%. The finished refined wax of this oil contentis removed by means of line 37 while the segregated oil is removed bymeans of line 38. This refined wax has a relatively wide boiling rangeas for ex ample in the range from about 320 F. to 585 P. (All boilingranges herein are at 10 mm. mercury absolute pressure.) In accordancewith the present invention, a portion of this wax is segregated by meansof line 39 and passed to a wax distillation zone 41. Temperature andpressure conditions are adjusted in zone 41 to segregate relativelynarrow cut refined wax fractions, as for ex ample a low boiling waxfraction boiling in the range from about 320 to 480 R, an intermediateboiling wax fraction boiling in the range from about 480 to 520 F., anda high boiling wax fraction boiling in the range from about 520 to 585F. The low boiling wax fraction is removed by means of line .42, theintermediate boiling wax fraction is removed by means of line 43, whilethe high boiling wax fraction is removed by means of line 44. Inaccordance with the present invention the narrow cut wax fraction,preferably the intermediate boiling range narrow cut wax fraction, isblended with the wide boiling refined wax removed by means of line 37.It is preferred that the amount of narrow cut wax utilized be in therange from about 40-70%, preferably in the range from about 40-60% byweight based upon the total wax.

The present invention is broadly concerned with an improved waxcomposition comprising a refined wax of a relatively wide boiling rangesuch as 320 F. to 585 F, having an oil content below about 1%,preferably below about 0.5%, in combination with a narrow cut refineddistilled wax fraction such as 480 F. to 520 F. which preferably has anaverage melting point substantially equivalent to the melting point ofthe wide cut fraction. The narrow cut distilled fraction has an oilcontent below about 1%, preferably below about 0.5%. In general, thespread between the initial and final boiling points of the wide boilingwax fraction is from about 200 F. to 300 F., while the spread of thenarrow cut fraction is from about 30 F. to F. A wax composition of thistype is particularly adapted for the coating of paper or other fibrousmaterials since it has a high blocking value and a high tensilestrength. While the invention has been described with rcspect tosecuring the narrow cut fraction by distillation, it is within theconcept to produce the narrow cut fraction by other segregation means,such as by fractional crystallization or by the use of selectiveprecipitating solvents to separate narrow cut wax fractions.

The process of the present invention will be more fully understood bythe following example illustrating the same:

EXAMPLE A sweated wax having an oil content below about .'5% was testedand its properties compared with the desired characteristics of a papercoating wax. A portion of this wax Was distilled to produce a narrow cutwax fraction. The waxes were then blended and the properties determined.The wax compositions produced met the required properties of a papercoating wax. The results of these operations are as follows:

Paraflin wax composition for paper coating IMPROVEMENT IN PHYSICALPROPERTIES OF PABAFFIW W'AX BY BLENDING NARROW AND WIDE BOiLlNG POINTWAX FRACTIONS Blends of Desir- Narrow Narrow Cut able Feed to Cut andFeed Inspections Physical Distilla- Distilled Proption 1 War ez'ties a65 3 50 4 35 4 50 Melting Point, F. 130132 132. 131. 0 131. 0 131.

Tensile Strength,

s. i. 70 F 300 390 70 270 300 (min) Blocking Point, F 100 95 100 102 100(min) Boiling Point Range, F. (595%) mm. Mercury Absolute Pressure 1Sweated paraflin refined wax.

2 Minimum temperature at which two strips of wax coated paper sticktogether when pressed under standard test conditions and then pulledapart. A marred wax surface is evident at blocking point.

3 Wt. percent N. C.

4 W17. percent feed.

What is claimed is:

1. Process for the manufacture of a wax composition suitable as afibrous coating material which comprises removing Waxy constituents froma waxy petroleum oil. treating said waxy constituents to reduce the oilcontent to below about 0.5% and to produce a wax fraction consistingessentially of constituents having a boiling range of about 320 F. toabout 585 F., at 10 mm. mercury absolute pressure, segregating said waxfraction into an initial and into a secondary stream, distilling saidinitial stream to segregate an intermediate narrow wax cut consistingessentially of constituents having a boiling range of about 480 F. to520 F. at 10 mm. mercury absolute pressure, blending said narrow wax cutwith said secondary stream boiling in the range from about 320 F. to 585F. in an amount of about to by Weight based on the total of the firstand second waxes.

2. An improved wax composition of an oil content of less than about 1%and which is suitable for the coating of fibrous materials whichcomprises a first refined paraffin wax consisting essentially ofconstituents having a boiling range of about 320 F. to about 585 F. at10 mm.

of mercury absolute pressure and a second refined paratfin waxconsisting essentially of constituents having a boiling range of about480 F. to about 520 F. at 10 mm. of mercury absolute pressure, theaverage melting points'of said wax constituents being substantiallyequal.

3. The composition of claim 2 wherein the average melting points of saidwax constituents are about 132 F.

4-. The composition of claim 2 wherein the amount of said first waxconstituent is in the range of from about 40% to 60% by weight based onthe total of the first and second waxes.

References Cited in the file of this patent UNITED STATES PATENTS2,467,959 Bowman 6: a1 Apr, 19, 1946 2,603,589 Schaerer July 15, 19522,611,734 Ridenour Sept. 23, 1952 2,624,501 Ferris Jan. 6, 19532,670,318 Halarnka et a1 Feb. 23, 1954 2,670,323 Hunter et a1 Feb. 23,1954

1. PROCESS FOR THE MANUFACTURE OF A WAX COMPOSITION SUITABLE AS AFIBROUS COATING MATERIAL WHICH COMPRISES REMOVING WAXY CONSTITUENTS FROMA WAXY PETROLEUM OIL, TREATING SAID WAXY CONSTITUENTS TO REDUCE THE OILCONTENT TO BELOW ABOUT 0.5% AND TO PRODUCE A WAX FRACTION CONSISTINGESSENTIALLY OF CONSTITUENTS HAVING A BOILING RANGE OF ABOUT 320* F. TOABOUT 585* F., AT 10 MM. MERCURY ABSOLUTE PRESSURE, SEGREGATING SAID WAXFRACTION INTO AN INITIAL AND INTO A SECONDARY STREAM, DISTILLING SAIDINITIAL STREAM TO SEGREGATE AN INTERMEDIATE NARROW WAX CUT CONSISTINGESSENTIALLY OF CONSTITUENTS HAVING A BOILING RANGE OF ABOUT 480* F. TO520* F. AT 10 MM. MERCURY ABSOLUTE PRESSURE, BLENDING SAID NARROW WAXCUT WITH SAID SECONDARY STREAM BOILING IN THE RANGE FROM ABOUT 320* F.TO 585* F. IN AN AMOUNT OF ABOUT 40% TO 60% BY WEIGHT BASED ON THE TOTALOF THE FIRST AND SECOND WAXES.
 2. AN IMPROVED WAX COMPOSITION OF AN OILCONTENT OF LESS THAN ABOUT 1% AND WHICH IS SUITABLE FOR THE COATING OFFIBROUS MATERIAL WHICH COMPRISES A FIRST REFINED PARAFFIN WAX CONSISTINGESSENTIALLY OF CONSTITUENTS HAVING A BOILING RANGE OF ABOUT 320* F. TOABOUT 585* F. AT 10 MM. OF MERCURY ABSOLUTE PRESSURE AND A SECONDREFINED PARAFFIN WAX CONSISTING ESSENTIALLY OF CONSTITUENTS HAVING ABOILING RANGE OF ABOUT 480* F. TO ABOUT 520* F. AT 10 MM. OF MERCURYABSOLUTE PRESSURE, THE AVERAGE MELTING POINTS OF SAID WAX CONSTITUENTSBEING SUBSTANTIALLY EQUAL.